In teaching a lesson out of Dr. Brad Edwards' "Lip Slurs" I was reminded of targets. Pete Norton used lip slurs to define an exact location of partials. He talked about the distance between notes and not over or under shooting these targets. Think of these on a vertical axis. Now think about exact slide positions on a horizontal axis. This might look like a fingering chart extending along your trombone, perpendicular to your body.
Of course you cannot actually see this chart on your trombone. In order to play "target practice" you have to use your ears to identify the targets and your embouchure, air, tongue, and arm to hit the targets.
But wait there is one more variable. Time. All of the systems used to produce pitch have to cooridinated in time with the music in order to hit the right target. In my lesson with Brandt Attema he made me subdivide my lips slurs to make the target smaller. This allowed less time for movement of any of these factors forcing a more coordinated approach to playing.
So now we have a 3D "target practice" Arm-horizontal, embauchure/air-vertical, time-time. All three of these have to be perfect to successfully hit a note. A physical representation of this "target practice" concept might look a little like a carnival game.
Except, of course, instead of using your eyes to see and lead the targets, you have to use you ears and mind. And instead of using your finger and a gun to fire bullets, you are using your air, embouchure, and instrument to fire notes.